The invention relates to self-locking devices for transmitting torque from a rotor to a tubular component or vice versa, especially for transmitting torque from a rotor to the core of a bobbin or the like. More particularly, the invention relates to improvements in so-called self-locking clamping chucks which can be inserted into tubular bodies prior to radial expansion to thereby ensure that the tubular body is compelled to rotate with the part or parts which drive the chuck.
The term "self-locking" is intended to denote clamping chucks and analogous torque transmitting devices of the type wherein one or more torque transmitting members can be arranged to move radially outwardly from the axis of a rotor in order to engage the internal surface of a tubular component (such as the core of a bobbin) if the tubular component is rotated while in contact with one or more torque transmitting members and while the rotor which is used to drive the torque transmitting members is braked.
German Auslegeschrift No. 1 574 438 discloses a clamping chuck wherein several torque transmitting members surround a shaft having a hexagonal cross-sectional outline and the torque transmitting members are biased radially toward the shaft by suitable springs. If the torque transmitting members are rotated with reference to the shaft or vice versa, the shaft bears against V-shaped internal surfaces of the torque transmitting members and moves them apart (i.e., away from the axis of the shaft) so that the external surfaces of the torque transmitting members can bear against the internal surface of a tubular component which surrounds the clamping chuck.
German Auslegeschrift No. 22 11 518 discloses a modified clamping chuck which employs a shaft having a square cross-sectional outline. The external surface of the shaft bears against the internal surfaces of the torque transmitting members, either directly or through the medium of rolling elements, to move the torque transmitting members apart. Such members are urged toward the periphery of the shaft by ring-shaped springs.
German Pat. No. 1 119 301 discloses a further clamping chuck wherein a supporting stud has recesses for pivotable torque transmitting members. These members become erected in response to the application of torque and then bear against the internal surface of a sleeve which surrounds the patented chuck.
All of the above described conventional clamping chucks exhibit the drawback that their torque transmitting action is not reliable, particularly that the torque receiving part which surrounds the torque transmitting members can be disengaged from these members in response to the application of shocks and vibrations which develop in actual use of the chuck. In other words, even minor stray movements can result in a termination of torque transmission between the internal surface of the tubular component and the external surfaces of the torque transmitting members. The main reason for such lack of reliability of the torque transmitting connection is believed to be that the extent of angular displacement of the tubular component relative to the torque transmitting members in order to establish a torque transmitting engagement between such parts is rather small. In other words, even a relatively small angular displacement of the aforementioned shafts with reference to the surrounding torque transmitting members suffices to bring about a pronounced radial displacement of the torque transmitting members which might be desirable and advantageous for rapid establishment of the torque transmitting connection but is a drawback when a relatively small angular displacement of the shaft in the opposite direction entails a termination of transmission of torque.